The complement system is a group of plasma proteins that when activated lead to target cell lysis and facilitate phagocytosis through opsonization. Complement is activated through a series of proteolytic steps by three major pathways: the classical pathway, which is typically activated by immune-complexes, the alternative pathway that can be induced by unprotected cell surfaces, and the mannose binding lectin pathway. All three pathways of complement cascade converge on proteolytic cleavage of complement component 5 (C5) protein. Cleavage of complement component 5 (C5) results in the production of fragments C5a and C5b, a process that is critical during the activation of the complement cascade. C5a can generate pleiotropic physiological responses through binding to its receptors (Monk et al 2007, Br. J. Pharmacol. 152: 429-448). C5a is a potent pro-inflammatory mediator that induces chemotactic migration, enhances cell adhesion, stimulates the oxidative burst, and induces the release of various inflammatory mediators such as histamine or cytokines. C5b mediates the formation of the membrane-attack complex (MAC, or C5b-9) leading to cell lysis in the late phases of the complement dependent cytotoxicity (CDC). Further, in nucleated cells that are resistant to cytolysis by C5b-9, sublytic quantities of C5b-9 can cause cellular activation which results in cell proliferation, generation of pro-inflammatory mediators and production of extracellular matrix.
Monoclonal antibodies to C5 are known in the art and have been described, for example, in US Patent/Publication Nos. 9206251, 9107861, 9079949, 9051365, 8999340, 8883158, 8241628, 7999081, 7432356, 7361339, 7279158, 6534058, 6355245, 6074642, 20160299305, 20160051673, 20160031975, 20150158936, 20140056888, 20130022615, 20120308559, and in WO2015198243, WO2015134894, WO2015120130, EP2563813B1, EP2328616B1, and EP2061810B1.
Fully human antibodies that specifically bind to C5 protein with high affinity and have improved pharmacokinetic properties could be important in the prevention and treatment of various C5-associated diseases (e.g., atypical hemolytic uremic syndrome).